Just as Google is synonymous with "search," Wikipedia is synonymous with "knowledge." This global online encyclopedia proves that the wiki format works well for managing knowledge. You can make a wiki of your own, too. Of course, your wiki doesn't have to be all-encompassing; it can focus on one particular topic or project, or serve as an interactive journal.
On Wikispaces, you'll find a simple way to get started with a collaborative wiki. With this online service, you can quickly set up your own public wiki, pick a theme, tweak the settings, and invite collaborators. The free plan includes up to 2GB of data, more than enough for most projects. You can't make a free wiki private--which means anyone can read your wiki--but only the collaborators you invite can edit it.
Not all wikis must be collaborative--or even public, for that matter. TiddlyWiki is a tiny personal wiki that resides in a single HTML document, with a small, optional Java applet on the side. TiddlyWiki costs nothing, can live in a Dropbox folder or on a USB stick, and works with pretty much any modern browser. It's customizable, as well, and it even has optional plug-ins. Your wiki is divided into individual topics called "tiddlers," which are ideal for storing tidbits of knowledge.
Desktop-Based Wiki Applications
Wikis aren't limited to the Web, either. Desktop wikis are full-fledged applications that offer easy-to-use text formatting and quick linking, but can be fast and nimble, not to mention private.
One well-known personal wiki is Tomboy, from the open-source GNOME project. Tomboy does everything it can to stay out of your way and just let you write: It automatically saves notes, and it makes links to existing topics magically appear. If only its installation routine were as magical--on Windows, Tomboy requires you to install the GTK# runtime before you can use it. On the plus side, it works on Linux (the OS it was meant for), as well as on Mac OS X. And Tomboy is unique in that each note resides in its own window.
A more conventional-looking wiki, Zim is also cross-platform (Windows and Linux), but it uses a single-document interface with a topic tree on the side. Although it is easier to install than Tomboy, it doesn't always offer instant results: Sometimes you need to reload the page before links start working.